1. Field of Use
The present invention relates to semiconductor devices such as ICs and LSIs having copper alloy leads.
2. Prior Art
Copper alloy lead materials for use in semiconductor materials are required to have the following properties:
(i) good workability for stamping;
(ii) heat resistance high enough to avoid thermal distortion and softening upon thermal bonding or thermal diffusion compression of a semiconductor device;
(iii) rapid heat dissipation and good electrical conductivity; and
(iv) strength and elongation great enough to avoid bending or failure due to the repeated bending that may occur during transportion of a semiconductor device or upon its installation in an electrical machine.
Characteristically, Cu alloy lead materials intended for use in specific fields are required to have the following values:
a tensile strength of 40 kgf/mm.sup.2 or more as an index of strength;
an elongation of 4% or more as another index of strength;
an electrical conductivity of 50% IACS or more as an index of heat dissipation and conductivity; and
a softening point of 400.degree. C. or higher as an index of heat resistance.
Many products have been proposed as Cu alloy lead materials satisfying these requirements and are currently in commercial use.
However, with the ever increasing demand for a higher packing density in modern semiconductor devices, Cu alloy lead materials are required to exhibit even higher degrees of strength and elongation in addition to high heat resistance and good heat dissipation and electrical conductivity. Therefore, it is strongly desired to develop Cu alloy lead materials that satisfy these requirements for performance.